Voice coil motors are used as actuators of electronic products (such as digital cameras, mobile phones, and digital cameras etc.) as they have small size, low price and save power.
As shown in FIG. 1, a conventional voice coil motor 1′ includes a housing 10′, a base 20′, a movable assembly 30′, four magnets 40′ around the movable assembly 30′, a top spring plate 50′ and a bottom spring plate 60′ located at the upper and lower surfaces of the movable assembly 30′ respectively. A cavity 12′ is defined by the housing 10′ and the base 20′, in which the movable assembly 30′ is installed. During the assembly of the voice coil motor 1′, upper and lower surfaces of the top spring plate 50′ are firmly connected with the housing 10′ and the magnets 40′ respectively, the movable assembly 30′ is configured between the top and bottom spring plates 50′, 60′, the bottom spring plate 60′ is fixed to the base 20′ which is firmly connected with the housing 10′. The movable assembly 30′ includes a lens holder 32′ and a coil 34′ winding on the lens holder 32′, and the lens holder 32′ is used for holding components such as lens barrel, focus lens or zoom lens, etc., and the top and bottom spring plates 50′, 60′ are used for protecting the lens barrel, focus lens or zoom lens. After the coils 34′ on the movable assembly 30′ is energized, magnetic force is generated between the coil 34′ and the magnets 40′, so that the movable assembly 30′ is moved in the cavity 12′ to change the distance between the components, such as lens barrel, focus lens or zoom lens, and a camera sensor, thereby focusing or zooming.
The base 20′ in FIG. 1 like a cover includes a cover edge 22′ connected with the housing 10′ and a connecting portion 24′ inserted into the cavity 12′ to connect with the second spring plate 60′. Thus the cover edge 22′ is protruded out of the housing 10′, which increases the total height and size of the voice coil motor. Furthermore, when the voice coil motor is applicable to cameras, the pixels will be restricted. By this token, the conventional thick voice coil motor can not meet the demand of thin and compact electronic products such as cameras, mobile phones, etc.
Thus there is a need to provide a thinner voice coil motor to overcome the drawbacks mentioned above.